Inclosed arc device



D66, 8, 1936. H PULFRICH 2,053,121

INCLOSED ARC DEVICE Filed May 24, 1932 fi l Fig 2 ZNVE N T UR fiCqzvs-i FULFF. ZC'H 5 525 A? T DANE Y Patented Dec. 8, 1936 UNETED STATES PATENT, OFFICE INCLO SED ARC DEVICE Hans Pulfrich, Berlin-Baumschulenweg,

Ger-

many, assignor to General Electric Company, a corporation of New York 4 Claims.

My invention relates to electric are lamps comprising refractory metal electrodes sealed in a transparent or translucent bulb or other envelope containing an inert gas. One of the objects of my invention is to provide a lamp construction which will produce a substantially uniform output of ultra-violet rays when operated in various positions. When used as a source of ultraviolet rays a globule of mercury is placed in the bulb and a filament is placed across the arc gap in multiple therewith to facilitate the starting of the arc. The electrodes across which the are forms are disposed perpendicular to the axis of the lamp so that the heat radiation from the the arc is greatest along said axis. With the present spheroidal bulb the lamp will produce a greater amount of ultra-violet rays when operated in a vertical position than when operated in a tilted position due to the fact that in the vertical position the mercury pool is directly in the path of greatest heat radiation. When the lamp is tilted the mercury pool moves out of the path of greatest heat radiation and the amount of ultra-violet ray radiation decreases with the degree of tilt. This variation is a disadvantage to any physician who may be using the lamp, since he will have difficulty in determining the duration of a treatment unless the lamp is operated in the same position continuously. According to my invention the output of ultra-violet rays is made substantially uniform by providing a bulb so shaped that the mercury pool will be at a greater distance from the are when the lamp is in a vertical position than when it is tilted. With this construction of the bulb, as the lamp is tilted the mercury pool moves closer to the are but it simultaneously moves further away from the path of greatest heat radiation with the result that said mercury pool is heated substantially uniformly in the various tilted positions of the lamp. Other features and advantages of my invention will appear from the following description of species thereof.

In the drawing Fig. 1 is an elevation of a lamp comprising my invention and Fig. 2 is a modification thereof.

Referring to Fig. 1, the lamp comprises a base In and bulb H composed of a glass transparent to ultra-violet rays such as quartz glass or borosilicate glass and containing an inert gas such as argon or nitrogen. Refractory metal electrodes l2, of tungsten or tantalum carbide or tantalum nitride, are mounted perpendicular to the axis of the lamp on support wires l3 in said bulb I I. Said support wires 13 are mounted on leading-in wires M which are sealed in a stem press IS. A filament I5 is mounted below the electrodes IE on the support wires 13, preferably hanging in loops ll therein to provide high contact resistances so that the arc will form initially across the electrodes l2 rather than across points on said filament. Said filament I6 is further supported by loops H3 in the ends of wires IS the opposite ends of which are sealed in a glass bead 20. Said bead 20 is supported by wires 2| mounted on the 1eading-in wires Hi.

The bulbs as used at present are spheroidal in shape as shown by 22 in dotted lines, whereas the bulb H comprising my invention, is elongated in the direction of the axis of the lamp so that the distance a from the center of the arc gap to the end of the bulb is approximately twice as great as the distance b from the center of the arc to the side of the bulb. A globule of mercury 23 in the bulb H is at a considerable distance from the are when the lamp is used in a vertical position so that the ultra-violet ray output is not as great as it would be in a spherical bulb 22. But when the lamp is tilted from the vertical, the mercury globule 23 moves closer to the arc gap and simultaneously further away from the path of greatest heat radiation, which is along the axis of the lamp, so that the ultraviolet ray output remains substantially the same. Tilting of the spherical bulb 22 would cause a marked reduction of the ultra-violet ray output.

Referring to Fig. 2, the bulb 24 is shaped as an ellipsoid with the longitudinal axis thereof coinciding with the axis of the lamp. The electrodes l2 are located in the transverse axis of said ellipsoidal bulb. As in Fig. l, the distance from the center of the arc to the tip of the bulb is approximately twice as great as the distance from said center of the arc to the side wall of the bulb. When the lamp is tilted the globule of mercury 23 approaches the arc and recedes from the axis or path of greatest heat radiation at a uniform rate so that this form of bulb is probably preferable to the form shown in Fig. 1.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. An inclosed arc lamp comprising a bulb adapted to transmit ultra-violet light and containing a body of mercury, a pair of leading-in wires sealed in the upper end of said bulb and projecting into the interior thereof, a pair of spaced metallic electrodes inside said bulb and secured one to each of said leading-in wires on opposite sides of the axis of said bulb, the arc gap between said electrodes being substantially perpendicular to said bulb axis and the greatest heat radiation from the arc during operation of the device being along said axis, and said bulb being elongated below the said are gap so that with the bulb in a vertical position the distance from the center of said arc gap to the surface of the mercury at the bottom of said bulb is substantially greater than the distance from the center of the arc gap to the side wall of said bulb, said bulb decreasing in diameter for the entire distance between the portion opposite the electrodes and the lower end thereof, the interior of said bulb below said electrodes being substantially unobstructed so as to permit emanations from said arc gap to pass directly through the walls thereof.

2. An inclosed arc lamp comprising a bulb adapted to transmit ultra-violet light and containing a body of mercury, a pair of leading-in Wires sealed in the upper end of said bulb and projecting into the interior thereof, a pair of spaced metallic electrodes inside said bulb and secured one to each of said leading-in wires on opposite sides of the axis of said bulb, the arc gap between said electrodes being substantially perpendicular to said bulb axis and the greatest heat radiation from the arc during operation of the device being along said axis, and said bulb being elongated below the said arc gap so that with the bulb in a vertical position the distance from the center of said arc gap to the surface of the mercury at the bottom of said bulb is substantially twice the distance from the center of the arc gap to the side wall of said bulb, said bulb decreasing in diameter for the entire distance between the portion opposite the electrodes and the lower end thereof, the interior of said bulb below said electrodes being substantially unobstructed so as to permit emanations from said are gap to pass directly through the walls thereof.

3. An enclosed are lamp comprising a bulb adapted to transmit ultra-violet light and containing a body of mercury, a pair of leading-in wires sealed in the upper end of said bulb and projecting into the interior thereof, a pair of spaced metallic electrodes inside said bulb and secured one to each of said leading-in wires on opposite sides of the axis of said bulb, the arc gap between said electrodes being substantially erpendicular to said bulb axis and the greatest heat radiation from the are during operation of the device being along said axis, the portion of the bulb below said are gap having the shape of an ellipsoid whose longitudinal axis coincides with the axis of the bulb, the longitudinal axis of said ellipsoid being substantially longer than the transverse axis thereof so that with the bulb in a vertical position the distance from the center of said arc gap to the surface of the mercury at the bottom of said bulb is substantially greater than the distance from the center of the arc gap to the side wall of said ellipsoidal bulb portion, the interior of said bulb below said electrodes being substantially unobstructed so as to permit emanations from said are gap to pass directly through the walls thereof.

4. An enclosed arc lamp comprising a bulb adapted to transmit ultra-violet light and containing a body of mercury, a pair of leading-in wires sealed in the upper end of said bulb and projecting into the interior thereof, a pair of spaced metallic electrodes inside said bulb and secured one to each of said leading-in wires on opposite sides of the axis of said bulb, the arc gap between said electrodes being substantially perpendicular to said bulb axis and the greatest heat radiation from the arc during operation of the device being along said axis, the portion of the bulb below said are gap having the shape of an ellipsoid whose longitudinal axis coincides with the axis of the bulb, the said electrodes being located in the transverse axis of said ellipsoid, and the longitudinal axis of said ellipsoid being substantially longer than the transverse axis thereof so that with the bulb in a vertical position the distance from the center of said are gap to the surface of the mercury at the bottom of said bulb is substantially twice the distance from the center of the arc gap to the side wall of said ellipsoidal bulb portion, the interior of said bulbbelow said electrodes being substantially unobstructed so as to permit emanations from said are gap to pass directly through the walls thereof.

HANS PULFRICH. 

